Method of manufacturing balloon catheter and balloon catheter

ABSTRACT

A method of manufacturing a balloon catheter involves applying a first application liquid, which contains a hydrophilic coating material, to the outer periphery of a balloon which is disposed on an elongated catheter and is held in an expanded state; folding the balloon; and applying a second application liquid, which contains the hydrophilic coating material, to the balloon with the balloon folded.

This application is a divisional of U.S. application Ser. No. 13/294,408files on Nov. 11, 2011, which is a continuation of InternationalApplication No. PCT/JP2010/057033 filed on Apr. 21, 2010, and claimspriority to Japanese Application No. 2009-117317 filed on May 14, 2009,the entire content of each of which is incorporated herein by reference.

TECHNOLOGICAL FIELD

The present invention generally relates to a balloon catheter and amethod of manufacturing a balloon catheter.

BACKGROUND DISCUSSION

Various medical procedures, for example PTA (percutaneous transluminalangioplasty) and PTCA (percutaneous transluminal coronary angioplastry),utilize a balloon catheter provided with an expandable and contractibleballoon.

Such a balloon catheter is used by inserting the balloon catheter into ablood vessel from outside a living body, and, when the balloon hasreached a stenosed part of the blood vessel serving as a target site,the balloon is expanded to expand the stenosed part. Since blood vesselsinto which the balloon catheter is inserted are generally accompanied bya sharp bend, stenosis or the like, the balloon catheter must exhibitlow-friction properties, trackability, anti-kinking properties, etc. Toenhance, by way of example, the low-friction properties, the catheter,particularly the balloon and the catheter body inserted into a bloodvessel, are coated with a hydrophilic material or the like. An exampleof this is described in Japanese Patent Laid-open No. Hei 8-24328.

In the conventional balloon catheters coated with a hydrophilicmaterial, however, the coating of the hydrophilic material issusceptible to peeling. For example, because the balloon is folded intoa small-sized form after the coating step, the coating may undergoexfoliation, leading to a lowered operationality.

SUMMARY

The balloon catheter disclosed here facilitates a reduction in thesliding resistance of the balloon so that the sling resistance isrelatively low, and exhibits excellent operationality. The ballooncatheter manufacturing method disclosed here makes it possible toproduce a balloon catheter having desirable characteristics.

A method of manufacturing a balloon catheter involves applying a firstapplication liquid, which contains a hydrophilic coating material, tothe outer periphery of a balloon which is disposed on a catheter, withthe first application liquid being applied while the balloon is in anexpanded state, folding the balloon, and applying a second applicationliquid, which contains a hydrophilic coating material, to the balloonwhile the balloon is folded.

In addition, in the method of manufacturing the balloon catheter, thefirst application liquid and the second application liquid are appliedunder different conditions.

The content of the hydrophilic coating material in the first applicationliquid is preferably lower than the content of the hydrophilic coatingmaterial in the second application liquid.

In addition, the method of manufacturing the balloon catheter preferablyinvolves satisfying the relationship 1<X2/X1≦100, where X1 [wt %] is thecontent of the hydrophilic coating material in the first applicationliquid and X2 [wt %] is the content of the hydrophilic coating materialin the second application liquid.

The method of manufacturing the balloon catheter can also involvecarrying out the application of the first and second application liquidsby dipping, with the rate of pulling up the balloon from the firstapplication liquid being lower than the rate of pulling up the balloonfrom the second application liquid in the second application step.

The method of manufacturing the balloon catheter can also be performedto satisfy the relationship 1<V2/V1≦20, where V1 [mm/sec] is the rate ofpulling up the balloon from the first application liquid and V2 [mm/sec]is the rate of pulling up the balloon from the second applicationliquid, is satisfied.

Another aspect involves a balloon catheter manufactured by themanufacturing method.

The balloon catheter includes a catheter, and a balloon disposed on thecatheter, wherein the balloon has a first hydrophilic coating layer onan outer surface thereof, and has a second hydrophilic coating layersurrounding the periphery of the balloon in the state of being folded insuch a manner as to be wrapped around the catheter.

The balloon catheter is preferably configured such that a fold of theballoon, which is in the folded state, overlaps with other part of theballoon, and the second hydrophilic coating layer is so provided as toextend across a boundary between the fold and the other part.

In addition, the thickness of the first hydrophilic coating layer ispreferably smaller than the thickness of the second hydrophilic coatinglayer.

The balloon is preferably folded so as to be wrapped around the outerperiphery of the catheter.

The method of manufacturing the balloon catheter preferably involvesapplying the first application liquid and the second application liquidby a method selected from the group consisting of dipping and spraying.

The method of manufacturing the balloon catheter preferably, furtherincludes cleaning the part coated with the first application liquid byuse of a cleaning liquid, with the balloon expanded, between the firstapplication step and the folding step.

In addition, the method of manufacturing the balloon catheter accordingto the present invention, preferably, further includes a heating stepfor mounting the balloon catheter to a member for maintaining the foldedstate of the balloon and subjecting the balloon in this state to aheating treatment, between the folding step and the second applicationstep.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

FIG. 1 is a perspective view of one example of a balloon catheter inaccordance with the disclosure here, with the balloon expanded.

FIG. 2 is a cross-sectional view of the balloon in a folded state.

FIG. 3 is a cross-sectional view of the balloon in an expanded state.

FIG. 4 schematically shows steps associated with one example of a methodof manufacturing a balloon catheter accordance with the disclosure here

DETAILED DESCRIPTION

FIGS. 1-3 illustrate one example of a balloon catheter in accordancewith the disclosure here, as well as the balloon used in the ballooncatheter. Features and aspects of the balloon and balloon catheterillustrated in the drawing figures are exaggerated to facilitate anunderstanding of the disclosure here, and so actual dimensions and thelike are not accurately reflected in the drawing figures.

The balloon catheter 1 shown in FIG. 1 as one example of the ballooncatheter in accordance with the disclosure here includes an elongatedcatheter 12, and a balloon 11 disposed on the catheter 12. The catheter12 includes a catheter body 13 which is flexible, and a hub 14 connectedto a proximal end (base end) of the catheter body 13. Thus, the ballooncatheter 1 is comprised of the flexible catheter body 13, the hub 14connected to the proximal end of the catheter body 13, and the balloon11 at the distal end portion (tip portion) of the catheter body 13. Theballoon 11 is firmly attached to the distal portion of the catheter body13 by, for example, fusing (welding), adhesion or the like.

The intermediate portion of the catheter body 13 is provided with anopening 133 for a guide wire. The catheter body 13 is provided thereinwith a first lumen 131 which communicates with the opening 133 and opensat the distal end of the catheter 12.

The hub 14 has a port 141 communicating with a second lumen inside thecatheter body 13. When a balloon-expanding fluid is injected via theport 141, the fluid is fed into the balloon 11 through the second lumenprovided inside the catheter body 13. This increases the internalpressure in the balloon 11 and thus expands the balloon 11. When theballoon-expanding fluid is drawn out of the balloon via the port 141,the fluid is discharged from the inside of the balloon 11 and so theballoon 11 contracts.

When the catheter 12 is in an unused state, the balloon 11 is keptcontracted and folded in such a manner as to be wrapped around an outerperiphery of the catheter body 13.

In addition, the balloon catheter 1 is provided, at least on the outersurface of the balloon 11, with a hydrophilic coating layer composed ofa hydrophilic material. Particularly, the balloon catheter 1 in thepresent embodiment has, as the hydrophilic coating layer, a firsthydrophilic coating layer 151 on the whole outer surface of the balloon11, and a second hydrophilic coating layer 152 provided so as tosurround the periphery of the balloon 11 when the balloon is in thefolded state in which the balloon 11 is wrapped around the catheter body13 as shown in FIG. 2. With the balloon catheter 1 thus having the firsthydrophilic coating layer 151 and the second hydrophilic coating layer152, excellent adhesion exists between the balloon 11 and thehydrophilic coating layer (the first hydrophilic coating layer 151 andthe second hydrophilic coating layer 152) composed of the hydrophilicmaterial. As a result, the balloon catheter 1 can be made excellent indurability, and sliding resistance can be kept relatively low even inthe case where frictional resistance is exerted repeatedly. When theballoon 11 is in the folded state, a comparatively thick hydrophiliccoating layer (a laminate of the first hydrophilic coating layer 151 andthe second hydrophilic coating layer 152) is exposed at a part or partsexposed to the outer surface (i.e., exposed to the outside), and acomparatively thin hydrophilic coating layer (the first hydrophiliccoating layer 151) is present at a part or parts which are folded to theinside (i.e., not exposed to the outside). This helps ensure that thefrictional resistance between portions of the balloon 11 (the frictionalresistance between portions of the first hydrophilic coating layer 151)at the part or parts folded to the inside is appropriately high. Thatis, in the balloon 11 in the folded state, frictional resistance at thepart or parts folded to the inside is greater than that at the exposedpart or parts of the balloon. As a result, even in the case where acomparatively high frictional force is exerted on the outer surface ofthe balloon 11 held in the folded state, the balloon 11 is relativelysecurely prevented from being unfolded or becoming out of shape.

In addition, in the present embodiment, when the balloon 11 is in thefolded state, the fold of the balloon 11 overlaps other parts of theballoon 11, and the second hydrophilic coating layer 152 is provided soas to extend across the boundary 111 between the fold and the other part(see FIG. 2). The boundaries 111 are the regions on the outer peripheryof the folded balloon between circumferentially adjacent folds as shownin FIG. 2. This helps ensure that when the balloon 11 is in the foldedstate, the hydrophilic coating layer (the second hydrophilic coatinglayer 152) provided so as to surround the outer periphery of the foldedballoon 11 is continuous. That is, the second hydrophilic coating layer152 covers the boundaries 111 so that the second hydrophilic coatinglayer 152 forms an uninterrupted (circumferentially continuous) outercoating on the folded balloon spanning the boundaries. As a result, evenin the case where a comparatively large external force or the like isexerted, for example, a chance of exfoliation of the hydrophilic coatinglayer is reduced or eliminated, so that the hydrophilic coating layer isparticularly insusceptible to peeling. In other words, the ballooncatheter 1 is particularly high in durability and reliability.

The thickness of the first hydrophilic coating layer 151 is preferablysmaller than the thickness of the second hydrophilic coating layer 152.This helps enable the balloon catheter 1 to be especially excellent indurability. Consequently, low sliding resistance can be maintained overa longer period of time, even in the case where frictional resistance isrepeatedly exerted on the balloon catheter 1.

Examples of the hydrophilic material (hydrophilic coating material)constituting the hydrophilic coating layer (the first hydrophiliccoating layer 151 and the second hydrophilic coating layer 152) includecellulose polymers, polyethylene oxide polymers, maleic anhydridepolymers (for example, maleic anhydride copolymers such as methyl vinylether-maleic anhydride copolymer), acrylamide polymers (for example,polyacrylamide, polyglycidyl methacrylate-dimethylacrylamide (PGMA-DMAA)block copolymer), water-soluble nylons, polyvinyl alcohol, andpolyvinylpyrrolidone.

Incidentally, while it suffices for the hydrophilic coating layer to beprovided at least on the outer surface of the balloon 11, it ispreferable for the hydrophilic coating layer to also be provided on theouter surface of the catheter body 13.

An example of method of manufacturing the above-described ballooncatheter 1 in accordance with the disclosure here is now set forth.

Referring to FIG. 4, the balloon catheter 1 described above can bemanufactured by a method that generally includes: a first applicationstep (1 a) involving applying a first application liquid 2 containing ahydrophilic coating material to the outer periphery of a balloon 11which is disposed on a catheter 12 and is held in an expanded state; acleaning step (1 b) involving cleaning the part of the balloon coatedwith the first application liquid 2 through use of a cleaning liquid 4while the balloon 11 is expanded; a folding step (1 c) involving foldingthe balloon 11; a heating step (1 d) in which the balloon catheter 1 ismounted to a tube 9 for maintaining the folded state of the balloon 11,with the balloon 11 in this state then being subjected to a heatingtreatment; a second application step (1 e) involving applying a secondapplication liquid 3, which contains a hydrophilic coating material, tothe balloon 11 while the balloon 11 is folded; and a containing step (1f) involving containing the balloon 11 in the folded state, into aprotective case (protective sheath) 8. Each of these steps is describedbelow in more detail.

<First Application Step>

This step may be any one which is carried out by applying the firstapplication liquid 2, which contains the hydrophilic coating material,to the balloon 11 which is disposed on the catheter 12 and which is heldin an expanded state. For instance, the first application step can becarried out by a method selected from the group consisting of dippingand spraying. In the present embodiment, among the above-mentionedmethods, dipping is used. Specifically, in the present embodiment, thefirst application step is carried out by dipping the entire balloon 11,in an expanded state and mounted on the catheter, and also dipping atleast a part of the catheter body 13, in the first application liquid 2contained in a tank 5 as shown in 1 a of FIG. 4. Adopting this aspect ofthe method helps ensure that, even where the first hydrophilic coatinglayer 151 to be formed is comparatively large in thickness,unintentional scattering of film thickness can be reliably inhibited orprevented from occurring, and productivity of the balloon catheter 1 canbe made particularly excellent.

The first application liquid 2 normally contains a solvent, in additionto the hydrophilic coating material (hydrophilic material). By utilizingthis, conditions such as viscosity of the first application liquid 2 areregulated to preferable values.

Examples of the solvent used in the first application liquid 2 includetetrahydrofuran (THF), dimethylformamide (DMF), and isopropyl alcohol(IPA).

The content of the hydrophilic coating material (hydrophilic material)in the first application liquid 2 is not particularly limited, but ispreferably 0.1 to 10 wt %, more preferably 0.1 to 5 wt %. Thiscontributes to the first hydrophilic coating layer 151 having acomparatively small thickness, while securely inhibiting or preventingunintentional scattering of film thickness from occurring. In addition,when the content of the hydrophilic coating material (hydrophilicmaterial) in the first application liquid 2 is in the above-mentionedrange, the first hydrophilic coating layer 151 can be formed to haveminute ruggedness (minute projections and recesses) on its outersurface. As a result, in the folded state of the balloon 11, the area ofcontact between portions of the surface of the balloon 11 folded to theinside (the surface where the hydrophilic coating layer is provided) isreduced, and so undesirable adhesion (blocking) or the like can berelatively securely prevented. The final balloon is thus not sosusceptible to potential problems at the time of expansion of theballoon 11. That is, the possibility of portions of the balloon stickingto one another in a way that would inhibit or prevent the balloon fromexpanding in the desired manner is avoided.

When dipping is used to apply the hydrophilic coating material to theballoon, after the balloon (and at least a part of the catheter body 13)is dipped into the first application liquid 2 in the tank 5, the coatedballoon is then pulled out of the liquid 2 in the tank 5. The rate ofpulling up the balloon 11 from the first application liquid 2 ispreferably 1 to 20 mm/sec, more preferably 1.67 to 16.7 mm/sec. Thisrate helps ensure that the first hydrophilic coating layer 151 with acomparatively large thickness is formed on the balloon, while relativelysecurely preventing unintentional scattering of film thickness fromoccurring. When the rate of pulling up the balloon 11 is in theabove-mentioned range, the first hydrophilic coating layer 151 can beformed to have the minute ruggedness (minute projections and recesses)on its surface as mentioned above. Consequently, in the folded state ofthe balloon 11, the area of contact between portions of the surface ofthe balloon 11 folded to the inside (the surface where the hydrophiliccoating layer is provided) is reduced, and generation of undesirableadhesion (blocking) or the like can be fairly reliably avoided orprevented. Accordingly, as mentioned above, in the balloon catheter 11obtained finally, generation of troubles at the time of expansion of theballoon 11 or the like can be more reliably avoided or prevented.

<Cleaning Step>

Following the first application step, with the balloon 11 held in anexpanded state, the part coated with the first application liquid 2 iscleaned by use of the cleaning liquid 4 generally shown at 1 b in FIG.4. This helps ensure that, for example, unintentional scattering of thethickness of the coating film formed from the first application liquid 2applied onto the balloon 11 is reduced, and smoothness can be enhancedappropriately.

This cleaning of the balloon can be carried out by use of a methodselected from the group consisting of dipping into the cleaning liquidand spraying of the cleaning liquid. In the present embodiment, dippingis adopted. Specifically, in the present embodiment, this step iscarried out by dipping the part coated with the first application liquid2 (the whole part of the balloon 11 and at least a part of the catheterbody 13) in the cleaning liquid while keeping the balloon 11 in theexpanded state as shown at (1 b) in FIG. 4. Adoption of such a methodmakes it possible to relatively assuredly obtain the above-mentionedbeneficial results.

<Folding Step>

Next, the balloon 11 is folded in such a manner as to be wrapped aroundthe outer periphery of the catheter body 13 as generally illustrated in1 c of FIG. 4. In the configuration shown in the drawing, the partswhich are folded are three parts. But the parts which are folded may betwo parts or may be four or more parts.

<Heating Step>

Subsequently, the catheter body 13 with the balloon 11 thereon ismounted in the tube 9 for maintaining the folded state of the balloon11, and the balloon 11 in this state is subjected to heating treatmentas depicted in 1 d of FIG. 4. This helps ensure that the shape and otheraspects or attributes of the first hydrophilic coating layer 151 formedfrom the first application liquid 2 are stabilized. This also helpsensure that, for example, the adhesion of the first hydrophilic coatinglayer 151 to the balloon 11 is quite good. In addition, carrying outthis step helps impart a folding tendency to the balloon 11, whereby theballoon can be relatively securely prevented from being unintentionallyunfolded at the time of inserting the finally obtained balloon catheter1 into a blood vessel or during subsequent manufacturing processes ofthe balloon catheter 1 (for example, during a second application step tobe described later).

<Second Application Step>

Next, the tube 9 is removed, and, while maintaining the balloon 11 inthe state in which it is folded, application of the second applicationliquid 3 containing a hydrophilic coating material is performed as shownat 1 e in FIG. 4.

Thus, the first application step in which the first application liquidcontaining a hydrophilic coating material is applied to the outerperiphery of the balloon held in the expanded state, and the secondapplication step in which application of the second application liquidcontaining a hydrophilic coating material is conducted with the balloonheld in the folded state, are both carried out. This helps ensure thatadhesion between the hydrophilic coating and the balloon is excellent,and the balloon catheter exhibits quite excellent durability, so thateven in the case where frictional resistance is exerted repeatedly, thesliding resistance can be kept relatively low.

In a case where application of the application liquid containing ahydrophilic coating material is conducted only with the balloon expandedor in the case where the application of the application liquid isconducted only with the balloon folded, the above-mentioned excellenteffects cannot be obtained.

Particularly in the case where the application of the application liquidcontaining a hydrophilic coating material is conducted only with theballoon folded, the adhesion between the balloon and the hydrophiliccoating layer is insufficient, so that troubles such as exfoliation of apart of the hydrophilic coating layer upon expansion of the balloon areliable to occur. In the case where the application of the applicationliquid containing a hydrophilic coating material is conducted only withthe balloon folded, the balloon catheter obtained would have a problemin that, when a comparatively large frictional force is exerted on theouter surface of the balloon in the folded state, such troubles asunfolding of the balloon or the balloon getting out of shape are moreliable to occur than in the case where the first application step isalso conducted.

In addition, in the case where the application of the application liquidcontaining a hydrophilic coating material is performed only with theballoon expanded, the hydrophilic coating layer may be peeled at thetime of folding the balloon. In addition, undesirable adhesion(blocking) or the like is liable to occur in the folded state of theballoon, resulting in the possibility of a degraded operationality atthe time of expanding the balloon, and unintentional deformation of theballoon may occur when the balloon is expanded. It might be thought thatthe above-noted problems can be addressed by reducing the amount of thehydrophilic coating material applied to the balloon. But, in that case,it would not be possible to sufficiently obtain the effect of provisionof the hydrophilic coating layer.

The second application step can be carried out, for example, by a methodselected from the group consisting of dipping and spraying. Among theabove-mentioned methods, dipping is adopted in the present embodiment.Thus, in the present embodiment, the second application step is carriedout by dipping the whole part of the balloon 11 in the folded state andat least a part of the catheter body 13 in the second application liquid3 contained in a tank 6 (see (1 e) of FIG. 4). With such a methodadopted, it is ensured that unintentional scattering of film thicknesscan be securely prevented from occurring in regard of the secondhydrophilic coating layer 152 obtained, and productivity of the ballooncatheter 1 can be made particularly excellent.

The second application liquid 3 normally contains a solvent, in additionto the hydrophilic coating material (hydrophilic material). By this,such conditions as viscosity of the second application liquid 3 arecontrolled to suitable values. As the solvent for constituting thesecond application liquid 3, there can be used such solvents asmentioned above as examples of the solvent constituting the firstapplication. In this case, the solvent constituting the firstapplication liquid 2 and the solvent constituting the second applicationliquid 3 may not necessarily have the same composition.

The present step (second application step) is preferably conducted indifferent conditions from those for the above-mentioned firstapplication step. This helps ensure that, in the state in which theballoon 11 of the finally obtained balloon catheter 1 is folded, theconditions of the hydrophilic coating layers (e.g., thickness, surfaceroughness, etc.) with respect to the part folded to the inside and thepart exposed to the outer periphery, of the outer surface of the balloon11, can respectively be controlled to suitable values.

Examples of those conditions (application conditions) adopted for thepresent step (second application step) which are set different from theconditions adopted for the first application step mentioned aboveinclude the composition of the application liquid (the composition ofthe hydrophilic coating material, the composition of the solvent, thecontent of the hydrophilic coating material, etc.), the rate ofpulling-up from the application liquid, and the treatment temperature.In addition, the present step (second application step) may be carriedout by an applying method different from that in the first applicationstep mentioned above. For instance, either the first application step orthe second application step may be carried out by dipping, and the otherapplication step may be carried out by spraying.

In the present embodiment disclosed by way of example, the secondapplication liquid 3 preferably possesses a higher content of thehydrophilic coating material than the first application liquid 2. Thishelps ensure that, in the state in which the balloon 11 of the finallyobtained balloon catheter 1 is folded, the smoothness of the hydrophiliccoating layer provided at that part of the outer surface of the balloon11 which is exposed to the outer periphery can be reliably made higherthan the smoothness of the hydrophilic coating layer provided at thatpart of the outer surface which is folded to the inside. As a result,sliding resistance at the time of inserting the balloon catheter 1 intoa blood vessel can be reduced, and such state can be maintainedsuitably. Moreover, operationality at the time of expanding the balloon11 of the balloon catheter 1 to the expanded state is quite excellent.

It is preferable that balloon catheter manufacturing method beimplemented to satisfy the relationship 1<X2/X1≦100, more preferably tosatisfy the relationship 1.5≦X2/X1≦50, where X1 [wt %] is the content ofthe hydrophilic coating material in the first application liquid 2 andX2 is the content [wt %] of the hydrophilic coating material in thesecond application liquid 3. This helps contribute to theabove-mentioned effects being exhibited more conspicuously.

The content of the hydrophilic coating material (hydrophilic material)in the second application liquid 3 is not particularly limited. Apreferably content is 0.1 to 10 wt %, more preferably 1 to 6 wt %. Whenthe balloon 11 of the balloon catheter 1 is folded, this helps ensurethat the film thickness of the hydrophilic coating layer at that part ofthe outer surface of the balloon 11 which is exposed to the outerperiphery (the sum of the film thickness of the first hydrophiliccoating layer 151 and the film thickness of the second hydrophiliccoating layer 152) is sufficiently large, and the second hydrophiliccoating layer 152 is able to exhibit excellent surface smoothness.

In addition, the rate of pulling up the balloon 11 from the secondapplication liquid 3 in the second application step is preferably sethigher than the rate of pulling up the balloon 11 from the firstapplication liquid 2 in the first application step. That is, the balloon11 is pulled up from the second application liquid 3 in the secondapplication step more quickly than the balloon 11 is pulled up from thefirst application liquid 3 in the first application step. By virtue ofthis, with the balloon 11 of the finally obtained balloon catheter 1folded, the smoothness of the hydrophilic coating layer provided at thatpart of the outer surface of the balloon 11 which is exposed to theouter periphery can be securely made higher than the smoothness of thehydrophilic coating layer provided at that part of the outer surfacewhich is folded to the inside. As a result, sliding resistance at thetime of inserting the balloon catheter 1 into a blood vessel can be madelower, and that state can be suitably maintained. Moreover,operationality at the time of expanding the balloon 11 of the ballooncatheter 1 to the expanded state is quite excellent.

The balloon catheter manufacturing method is also preferably implementedto satisfy the relationship 1<V2/V1≦20, more preferably to satisfy therelationship 1.05≦V2/V1≦10, where V1 [mm/sec] is the rate of pulling upthe balloon 11 from the first application liquid and V2 [mm/sec] is therate of pulling up the balloon 11 from the second application liquid.This contributes to the above-mentioned effects being exhibited moreconspicuously.

The rate of pulling up the balloon 11 from the second application liquid3 is preferably 1 to 20 mm/sec, more preferably 5 to 19 mm/sec. In thestate in which the balloon 11 of the balloon catheter 1 is folded, thishelps ensure that the film thickness of the hydrophilic coating layer(the sum of the film thickness of the first hydrophilic coating layer151 and the film thickness of the second hydrophilic coating layer 152)provided at that part of the outer surface of the balloon 11 which isexposed to the outer periphery is sufficiently large, and the secondhydrophilic coating layer 152 exhibits particularly excellent surfacesmoothness.

After the present step (second application step), a drying treatment(e.g., an air-drying treatment) may be carried out to, for example,remove the solvent or the like present on the balloon 11 or the like,prior to the containing step which will be described below.

<Containing Step>

Subsequently, the balloon 11 in the folded state is contained or placedin a protective case (protective sheath) 8 (1 f). As a result of this,the desired balloon catheter 1 is obtained.

While an embodiment of the balloon, balloon catheter and method ofmanufacture have been described above, the invention is not limited tosuch embodiment.

For instance, the configuration of each of the components of the ballooncatheter can be replaced with an arbitrary configuration that canexhibit the same or similar function. And other features and/or aspectsmay be added.

In addition, while the first application step and the second applicationstep have been described to be each carried out once in the aboveembodiment, the first application step and/or the second applicationstep may be carried out two or more times. For instance, a process maybe adopted in which the first application step is conducted a pluralityof times, thereafter the folding step is performed, and then the secondapplication step is further carried out a plurality of times. Inaddition, a series of steps including the first application step, thefolding step and the second application step may be repeated a pluralityof times.

The description set forth above explains that the first application stepand the second application step are conducted under differentconditions. But the first application step and the second applicationstep may be carried out under the same conditions. In addition, thedescription above explains that the content of the hydrophilic coatingmaterial in the first application liquid used in the first applicationstep is lower than the content of the hydrophilic coating material inthe second application liquid used in the second application step, andthe rate of pulling up the balloon from the first application liquid inthe first application step is lower than the rate of pulling up theballoon from the second application liquid in the second applicationstep. However, the combination of the conditions for the firstapplication step with the conditions for the second application step isnot restricted to the above-mentioned combination. In this case, aneffect or effects according to the combination of the conditions areobtained.

EXAMPLES

Now, specific examples of the present invention will be described below.

[1] Manufacture of Balloon Catheter Example 1

First, a balloon formed from a polyamide elastomer was prepared. Theballoon was joined to a tip (distal) portion of a catheter body formedfrom a polyamide elastomer by fusing (welding), and a hub was connectedto the base end (proximal end) of the catheter body.

Next, with the balloon expanded, immersion (dipping) of the whole partof the balloon (i.e., the entire balloon was immersed or dipped) and apart of the catheter body in a first application liquid containing ahydrophilic coating material was conducted, thereby to apply the firstapplication liquid to these parts (first application step). The firstapplication liquid used here was composed of a dimethylacrylamide(DMAA)-glycerol methacrylate (GMA) copolymer as the hydrophilic coatingmaterial and tetrahydrofuran (THF) as a solvent. The content X1 of thehydrophilic coating material in the first application liquid was 1.5 wt%. In addition, the rate V1 of pulling up the balloon from the firstapplication liquid was 13.3 mm/sec.

Next, with the balloon expanded, the whole part of the balloon and apart of the catheter body were immersed in water used as a cleaningliquid, and the parts coated with the first application liquid werecleaned (cleaning step).

Thereafter, the parts to which the first application liquid and thecleaning liquid were applied were air-dried, and the balloon was wrappedaround the outer periphery of the catheter body (folding step).

Subsequently, a plastic-made tube was mounted on the outer periphery ofthe balloon thus folded, so as to maintain the folded state of theballoon, and, in this state, the folded balloon on the tube wassubjected to a heating treatment (heating step).

Next, the tube was removed, and, in that state (the state in which theballoon was folded), immersion (dipping) of the whole part of theballoon (i.e., the entire balloon was immersed or dipped) and a part ofthe catheter body in a second application liquid containing ahydrophilic coating material was performed, thereby to apply the secondapplication liquid to these parts (second application step). The secondapplication liquid used here was composed of dimethylacrylamide(DMAA)-glycerol methacrylate (GMA) copolymer as the hydrophilic coatingmaterial and tetrahydrofuran (THF) as a solvent. The content X2 of thehydrophilic coating material in the second application liquid was 1.5 wt%. In addition, the rate V2 of pulling up the balloon from the secondapplication liquid was 13.3 mm/sec.

Thereafter, the parts to which the second application liquid was appliedwere air-dried, and the balloon in the folded state was contained intoor placed in a plastic-made protective case (protective sheath), therebyto obtain the desired balloon catheter (containing step).

Example 2

A balloon catheter was manufactured in the same manner as in Example 1,except that in the second application step an application liquid havinga content X2 of the hydrophilic coating material of 3.0 wt % was used asthe second application liquid and the rate V2 of pulling up the balloonfrom the second application liquid was 15.0 mm/sec.

Comparative Example 1

A balloon catheter was manufactured in the same manner as in Example 1,except that the second application step was omitted. Specifically, inthis comparative example, application of the hydrophilic coatingmaterial was conducted only with the balloon expanded, and applicationof the hydrophilic coating material was not performed with the balloonfolded.

Comparative Example 2

A balloon catheter was manufactured in the same manner as in Example 1,except that the first application step, the cleaning step and theheating step were omitted. Specifically, in this comparative example,application of the hydrophilic coating material was conducted only withthe balloon folded, and application of the hydrophilic coating materialwas not carried out with the balloon expanded.

[2] Evaluation

For each of the balloon catheters obtained in the Examples and theComparative Examples above, slidability was evaluated in the followingmanner.

First, the balloon of each of the balloon catheters obtained in theExamples and the Comparative Examples was immersed in water.

Next, a hole was bored in a silicone valve (made by Dow CorningCorporation; 1 mm in thickness), and a stainless steel wire was passedtherethrough.

Next, the balloon catheter was inserted along the stainless steel intothe valve body, starting from the distal side of the balloon catheter,and the balloon catheter was so positioned that the boundary between atapered portion and a straight portion of the balloon made contact withthe valve body.

In this state, a sliding test was conducted under the conditions of avelocity of 500 mm/min and a stroke of 10 mm.

The sliding test was performed by a method in which 50 reciprocationswere made for one set, the above-mentioned sliding operation wasrepeated for five sets, and the load acting on the balloon catheterduring the sliding was measured on an autograph. The silicone valve bodywas replaced upon completion of each set.

[2-1] Sliding Resistance at First-Time Sliding in the First Set

For each balloon catheter obtained in the Examples and the ComparativeExamples above, the sliding resistance (the load acting on the ballooncatheter) at the time of the first-time sliding in the first set wasdetermined, and evaluation thereof was conducted according to thefollowing criterion.

A: Sliding resistance (the load acting on the balloon catheter) is lessthan 10 gf

B: Sliding resistance (the load acting on the balloon catheter) is notless than 10 gf and less than 12 gf

C: Sliding resistance (the load acting on the balloon catheter) is notless than 12 gf and less than 14 gf

D: Sliding resistance (the load acting on the balloon catheter) is notless than 14 gf

[2-2] Increment in Sliding Resistance

For each of the balloon catheters obtained in the Examples and theComparative Examples above, the difference between the slidingresistance (the load acting on the balloon catheter) at the time of thefinal-time sliding in the fifth set and the sliding resistance (the loadacting on the balloon catheter) at the time of the first-time sliding inthe first set (the increment in sliding resistance) was determined, andevaluation thereof was conducted according to the following criterion.

A: Increment in sliding resistance is less than 7 gf

B: Increment in sliding resistance is not less than 7 gf and less than15 gf

C: Increment in sliding resistance is not less than 15 gf and less than40 gf

D: Increment in sliding resistance is not less than 40 gf

The results of the evaluations above are shown in Table 1.

TABLE 1 Sliding resistance at first- Increment in sliding time slidingin first set resistance Example 1 A A Example 2 A A Comparative A DExample 1 Comparative B D Example 2

The results in Table 1 show that in each of the Examples utilizing theballoon catheter and manufacturing method disclosed here, the slidingresistance of the balloon was kept low even when a frictional resistancewas exerted repeatedly, indicating that the balloon catheter exhibitsexcellent durability. In contrast, in the Comparative Examples, thesliding resistance rose greatly when a frictional resistance was exertedrepeatedly, indicating that the balloon catheter possesses poordurability.

The method of manufacturing a balloon catheter according to thedisclosure here includes: applying a first application liquid, whichcontains a hydrophilic coating material, to the outer periphery of aballoon which is disposed on a catheter and is held in an expandedstate; folding the balloon; and applying a second application liquid,which contains a hydrophilic coating material, to the balloon with theballoon folded. Therefore, it is possible to provide a method ofmanufacturing a balloon catheter by which the sliding resistance on theballoon is kept low and a balloon catheter excellent in operationalitycan be suitably manufactured.

The detailed description above describes features, aspects andcharacteristics of a balloon catheter and method of manufacturing aballoon catheter as disclosed here. The invention is not limited,however, to the precise embodiment and variations described above andillustrated in the drawing figures. Various changes, modifications andequivalents could be effected by one skilled in the art withoutdeparting from the spirit and scope of the invention as defined in theappended claims. It is expressly intended that all such changes,modifications and equivalents which fall within the scope of the claimsare embraced by the claims.

What is claimed is:
 1. A method of manufacturing a balloon cathetercomprising: applying a first application liquid, which contains ahydrophilic coating material, to an outer periphery of a balloon whichis disposed on a catheter, the first application liquid being appliedwhile the balloon is in an expanded state; folding the balloon; andapplying a second application liquid, which contains a hydrophiliccoating material, to the balloon while the balloon is folded, whereinthe hydrophilic coating material contained in the first applicationliquid is identical with the hydrophilic coating material contained inthe second application liquid.
 2. The method of manufacturing theballoon catheter according to claim 1, wherein application of the firstapplication liquid and application of the second application liquid arecarried out under different conditions.
 3. The method of manufacturingthe balloon catheter according to claim 1, wherein a content of thehydrophilic coating material in the first application liquid is lowerthan the content of the hydrophilic coating material in the secondapplication liquid.
 4. The method of manufacturing the balloon catheteraccording to claim 3, wherein the content of the hydrophilic coatingmaterial in the first application liquid relative to the content of thehydrophilic coating material in the second application liquid satisfiesthe relationship 1<X2/X1≦100, where X1 [wt %] is the content of thehydrophilic coating material in the first application liquid and X2 [wt%] is the content of the hydrophilic coating material in the secondapplication liquid.
 5. The method of manufacturing the balloon catheteraccording to claim 1, wherein the first application liquid and thesecond application liquid are both applied by dipping; furthercomprising pulling up the balloon from the first application liquidafter applying the first application liquid by dipping; pulling up theballoon from the second application liquid after applying the secondapplication liquid by dipping; and wherein a rate of pulling up theballoon from the first application liquid is lower than the rate ofpulling up the balloon from the second application liquid.
 6. The methodof manufacturing the balloon catheter according to claim 5, wherein therate of pulling up the balloon from the first application liquidrelative to the rate of pulling up the balloon from the secondapplication liquid satisfies the relationship 1<V2/V1≦20, where V1[mm/sec] is the rate of pulling up the balloon from the firstapplication liquid and V2 [mm/sec] is the rate of pulling up the balloonfrom the second application liquid.
 7. The method of manufacturing theballoon catheter according to claim 1, wherein the first applicationliquid and the second application liquid are applied in different ways.8. A balloon catheter manufactured by the manufacturing method accordingto claim
 1. 9. The method of manufacturing the balloon catheteraccording to claim 1, wherein the thickness of the first hydrophiliccoating layer is smaller than the thickness of the second hydrophiliccoating layer.
 10. The balloon catheter according to claim 8, whereinthe thickness of the first hydrophilic coating layer is smaller than thethickness of the second hydrophilic coating layer.